1. Technical Field
This invention relates to the field of antireflective coatings. More specifically, the invention relates to an acid sensitive antireflective coating and its method of use.
2. Background Art
In the production of semiconductor devices, an integrated circuit substrate is coated with a film of photo patterning resist, exposed to actinic radiation, and developed to define a resist image over the integrated circuit substrate. The resist image includes both lines and spaces, wherein portions of the photo patterning resist that are removed form the spaces and the portions that remain form the lines. The resist image is transferred to the integrated circuit substrate by modifying the exposed portion of the substrate. Such modification may be performed by removal of a portion of the substrate by etching processes, by implantation of atomic species into the substrate, or by other methods known to those skilled in the art. During such processes, the photo patterning resist lines act as a mask to prevent modification of the portions of the substrate underlying the resist lines. Resolution of the image transferred to the substrate is dependent on the resolution of the resist image.
During exposure of a photo patterning resist on an integrated circuit substrate, some reflection of the actinic radiation off the integrated circuit substrate will typically occur. The reflection causes film interference effects that change the effective exposure intensity within a chip, across the wafer, and from wafer to wafer. Given the variation in effective exposure intensity, an unacceptable amount of line width variation typically occurs. This is especially true in modem manufacturing where laser exposure tools are used as the source of the actinic radiation and reflection is particularly prevalent.
To prevent reflection of actinic radiation into a photo patterning resist, one or more layers of an antireflective coating (ARC) may be provided between a substrate and a photo patterning resist film. ARCs often include a radiation adsorbing dye dispersed in a polymer binder, however, some polymers exist that contain an appropriate chromophore that sufficiently adsorbs the actinic radiation such that an additional adsorbing dye is not required. The ARC may be adapted to attenuate a particular wavelength of radiation used to expose the photo patterning resist by a selection of suitable adsorbing dies or a polymer having suitable chromophores.
Unfortunately, the use of an ARC creates its own problems. Once the photo patterning resist film is developed, exposing the underlying ARC, the ARC must be removed to expose the underlying integrated circuit substrate for subsequent modification as mentioned above. Commonly, the ARC is removed using a reactive ion etch process, however, other types of dry etching or wet etching as known to those skilled in the art may be used.
Regardless of the method selected for removing the ARC, there is a strong tendency for such processes to degrade the resist image by rounding off the comers, changing the line width, and creating other nonuniformities across the wafer or wafer to wafer. In particular, such processes may result in undercut and possible partial liftoff of the photo patterning resist film, causing etch bias, profile changes, photo patterning resist thinning, and other photo patterning resist defects as described in U.S. Pat. No. 5,635,333, issued to Petersen et al. While Petersen et al., and perhaps other references, attempt to resolve a portion of the above described problems, they are only partially effective at doing so.
Therefore there existed a need to provide a method and/or composition for forming an ARC that may be removed without degrading the resist image and that provides simplification of the complex processing steps recited by Petersen et al. and perhaps other references.